Reduced-Scaling Quantum Mechanical Response Theory for the Spectroscopic Properties of Molecules in Solution

弗吉尼亚理工学院和州立大学的T.Daniel Crawford教授得到了化学理论、模型和计算方法计划的支持，他开发计算工具来预测溶液中手性分子的光学性质。手性分子有相同的原子以不同的顺序连接。手性分子不能叠加在它们的镜像上。有“左撇子”和“右撇子”两种形式，每一种形式都将光波变成不同的方向。了解手性分子对制药工业特别重要，因为一种手性形式可能具有很大的药用价值，而另一种形式可能没有价值或有毒。准确预测溶解在液体中的手性分子的光学性质对于计算化学来说是一项艰巨的任务。虽然简单分子性质的计算机模型已经很好地建立了，但手性分子与光的相互作用即使对于最先进的计算方法也是独特的挑战。在这项研究项目中，克劳福德教授和他的同事开发了健壮而准确的计算技术，这些技术比目前的方法所需的时间更少。这些计算工具使研究人员能够了解手性分子结构和它们与光的相互作用之间的关系。这些新工具为化学界提供了更深入的了解分子与光相互作用的方式。该研究计划通过对研究生和本科生进行基础理论和量子化学方法开发方面的教育和培训，使更广泛的计算科学领域受益。在这个项目中开发的软件包括在PSI4中，这是一个广泛使用的计算化学包，社区可以免费获得。克劳福德博士是PSI4的主要开发者之一。丹尼尔·克劳福德和他的同事通过互补的方法简化了耦合团簇理论，促进了对液体中手性的高精度建模。他们建立在缩小尺度方法的基础上，以开发“扩展局部对-自然-轨道”方法的生产级实现，在该方法中，每对定域占据轨道的相关域是基于通过近似二阶场扰动密度计算的自然轨道构建的。Crawford小组正在扩展他们最近的合作工作，开发一种“图解”随机耦合集群方法，该方法将高精度耦合集群方法的解决方案的存储成本降低100倍(通过四次激发)。他们证明，引入随时间变化的外电场产生的波函数稀疏性比场扰动波函数的稀疏性大得多，之后他们正在开发一种局部相关的实时耦合集群方法，可以利用现有的线性缩放框架。这些新模型的开发涉及与实验者和理论家的大量、成熟的合作。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Professor T. Daniel Crawford, of Virginia Polytechnic Institute and State University is supported by an award from the Chemical Theory, Models and Computational Methods program to develop computational tools to predict the optical properties of chiral molecules in solution. A chiral molecule has the same atoms connected in a different order. Chiral molecules cannot be super-imposed on their mirror image. There is a "left-handed" and a "right-handed" form each of which turns the waves of light into different directions. Understanding chiral molecules is especially important to the pharmaceutical industry as one chiral form may be of great medicinal value, while the other form may be of no value or toxic. The accurate prediction of the optical properties of chiral molecules dissolved in liquids is a daunting task for computational chemistry. While computer models of simple molecular properties are well established, interactions of chiral molecules with light present unique challenges even for state-of-the-art computational methods. In this research project, Professor Crawford and coworkers develop robust and accurate computational techniques that take less time than current methods. These computational tools allow researchers to understand the relationship between chiral molecular structures and their interactions with light. The new tools provides the chemistry community with a deeper understanding how molecules interact with light. This research program benefits the larger field of computational science through the education and training of graduate and undergraduate students in the fundamental theory and development of quantum chemical methods. Software developed during this project is included in PSI4, a widely used computational chemistry package that is freely available to the community. Dr. Crawford is one of the lead developers of PSI4.Daniel Crawford and coworkers advance the high-accuracy modeling of chiroptical properties in the liquid phase by streamlining coupled cluster theory through complementary approaches. They build upon reduced-scaling methods to develop production-level implementation of an "extended local-pair-natural-orbital" approach, in which the correlation domain for each pair of localized occupied orbitals is constructed based on natural orbitals computed via an approximate second-order field-perturbed density. The Crawford group is extending their recent collaborative work on the development of a "diagrammatic" stochastic coupled cluster approach that exhibits a hundred-fold reduction in the memory costs for the solution of high-accuracy coupled cluster methods (through quadruple excitations). Following their demonstration that the introduction of a time-dependent external electric field yields substantially greater wave function sparsity than that of the field-perturbed wave function, they are developing a locally correlated real-time coupled cluster approach that can take advantage of existing linear-scaling frameworks. Development of these new models involves numerous, well-established collaborations with both experimentalists and theorists.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.